Metallurgical heat treating



Feb. 9, 1932.

J. KOHLMEYER METALLURGICAL HEAT TREATING Fi 1ed April 26, 1928 lill ltd

Patented heh., Q, 1932 untreu STATES lflW' YRK, N.. Y., A-ORIPORATION 0I" NEW .duplication dprll :'26, ltlt, llicrlal llo.

lhis iiirention relates to a .rnethod for producing metals, especially lead, l'rorn ores, condensed sniolres and tueries, residues and the lilre.

llres, condensed turnos and dying duets, residues and similar raw materials, containing instal or inetal compounds are usually inolten donn in a reducing atmosphere in shalt lrilns. Condensed iz'urnes and srnolres und siinilur ldnely divided materials are gen erally agglomerated into lumps, betere charging thern into the lriln. Pure lead ores hare lor a number of years also been suhdented, to a hearth renning process lor the direct production of lead, thus avoiding lriln processes. 'llhis hearth process however requires manual labor and gives residues still rich in lead..

'llhe nerr niethod according to the intenm tion, which is simple in operation and leads to Igoed yields of metal, is carried out in a rerolring cylinder furnace, provided with' an interior round or cornered refractory linllhe accompanying drawings illustrate two types ot lurnaces which are adapted for carrying out this invention.

lzlig. l shows diagrammatically one fornil el suitable apparatus, the furnace being shown in vertical longitudinal section;

llig. 2 is a modified form of furnace, in which only the charging end is shown, in vertical longitudinal section, and y lllig. 3 is an elevation of the charging end et the furnace shown in Fi 2. At the front side of the cylindrical furnace A is arranged a burner b for oil, coal dust p er gas in such a manner, that the llame enters the interior of the furnace A by the opening o, thus heating the furnace to a temperature necessary for the reduction of lead oxide or the decomposition of lead sulfate. The combustion gases leave the furnace A either at the opposite side by a central opening o or by a canal d with slide valve Zat the burner side. In the latter case the opening c is closed by a cover e. The combustion ases are thus forced to pass the interior o the furnace twice. 0n the Way from the burner side tox the opposite side of the furnace there burns dmdlll', und ln Germany April 53B, 192?.

a llame under pressure in the furnace.. This llame together with noncornbusted gases and air heats the Wall of the furnace opposite the burner side, is mired there with the noncornbusted gases and air and forced upwards into a cone, in which there is no pressure or draft and Where the combustion is completed. 'llhe draft produced hy the chimney in the canal d' is regulated in such a manner, that the aero zone of the gas pressure in the lur-` nace is just above the entrance opening u.

llt is Very important, that the clear diurneter of the cylinder Afurnace be greater than its clear length; at least however the clear diameter of the 'furnace must be the same as the clear length, as only thus is it possible tuv to heat the furnace Walls to the necessary temperature, namely, light red heat.

When the interior of the furnace has heen heated to the necessary temperature, the raw material, from Whichlead is to be produced, is charged into the furnace by a charging device it arran ed at the burner or the opposite front side cfg the furnace. The charging olerice 7c is connected with/a condensing chanr' the rotation of the furnace; the slag is thereby pressed away from the rotating part of the cylinder wall, thus avoiding passage of the doughy slag through the joint between the statlonary insertion piece and the rotating furnace. This liquid metal produced is drawn oi through the tap hole h (Fig. 1).

The burner has to be 4operated such a time, that also the charged material has taken up the temperature present in the the furnace. Then reducing carbon such as granulated coke, ground coal, charcoal or the like is charged into the furnace by the charging device lc. Also liquid oil may be interior of atomized by the burner b into the and acts as reducing agent. The reducing material charged into the furnace is then also to be heated to the temperature present in the rotated during the charging o eration. If

\ ide.

this is not the case rotation o the furnace must however begin as soon as the charging operation of the furnace is Ecompleted. At this moment the action of the burner may be vdecreased as much as possible, as the heat accumulated by the brick lining of the furnace is sufficient t0 keepthe reduction process of the raw material going for a certain time. The canal d and all the other open parts of the furnace are to be kept closed as much as possible durin the reduction of the lead ox- When t e heat accumulated by the brick linin of the furnace is spent and used and the re uction process is not finished yet, the slide valve Z of the canal d has to be opened and the burner b is started carefully again, in order to keep the reduction temperature in the interior of the furnace. This careful heating is necessary, in order to avoid an overheatin in the interior of the furnace which wou d lead to an undue evaporation of lead oxide due to a greater amount of combustion gasespresent in the furnace.

The small amounts of lead and lead oxide evaporated during the reduction process are recovered again in the condensing chamber z' behind the furnace. The condensing chamber z' may be of any kind such as with bags or electrically operated. From this condensling chamber z the condensed product is automatically brought back again into the furnace.

When volatile products of different kind are leaving the furnace during the reduction process they may be recovered and brou ht ack separately into the furnace. The ollowing example mag serve to illustrate this separate recovery: zinc or cadmium or arsenic containing lead oxide is condensed in an electrically operated condensing apparatus. This impure for instance zinc containin lead oxide, named hereinafter the main oxide, is reduced in the revolvingiurnace to lead, the zinc oxide, named hereinafter the secondary oxide, being volatilized during the reduction rocess. This ,zinc oxide is condensed in t e same electrically operated con- .l densing chamber and brought back together with fresh main oxide into the revolving furnace. This procedure is repeated so often, until the fresh main oxide is rich in zinc oxide. When this is the case, the volatilized zincoxide is condensed in a second electrically operateda condensing chamber, and brought back into a revolving furnace so often, until zinc oxide free from lead is obzinc oxide, cadmium oxide or arsenic acid on the other hand are obtained. The new method is of especialv importance 4for working up fine smokes, fumes and dusts condensed in electrically operated gas cleaning or dust condensing chambers, which until now had to be agglomerated into lumps, before charging them together with fluxes into kilns. According to the invention these raw materials may be charged directly from a central` condensing chamber into the revolving furnace connected with the condensing chamber. Also the addition of fluxes is not necessary. The lead is directly recovered as metal by a single step operation inthe revolving furnace connected with the condensing chamber.

When the lead containing raw materials alsoI contain sulfur as lead sulfate or lead sulfide or both, it is possible to obtain lead without addition of carbon according to the following equations 1 bso,.= 1 to+so s PbS 2PbO 3Pb SO2.

Lead sulfate may also be reduced to lead sulfide by addition of carbon. If residues of lead oxide remain in the furnace, carbon has to be added. If however residues of lead sulfide are present in the furnace, the amount oflead oxide necessary -for the reaction with the lead sullide may be produced by blowin air into the furnace. the device are therefore adapted for recovering all the lead presentin any form in the raw material. In any case-one has to watch that the furnace does not become too hot, in order to'avoid volatilization of too great an amount of lead, although this is always recovered. Too high a temperature in the furnace must also be avoided, in order'to prevent the lead compounds from becoming very liquid and from forming silicates with the brick lining of the furnace which would result in the destruction of the lining. The content of the furnace must always have a doughy consistence, thus obtainin a good mixture of the raw material with te carbon andd a satisfactory reduction of the lead 0x1 e.

The new method an The new method is also suitable for the i treatment of raw materials containin other metals than lead. Thus for example t e new method may be employed especially for those metallurgical reactions, carried through until now in avery uneconomical manner in flame furnaces or kilns. By the simultaneous mixing and heating of the content of the furnace through-the flames and combustion gases from above and the hot walls of the revolving furnace from below the rate of reaction is increased considerably. Thus for liti till! lill nannies and ditticultly reducible metal oxides may be treated, lor errample, a mixture ot lead oxide and amc oiride, in which case the dnlicultly reducible Zinc orrido requiring a high temperature tor reduction is enriched in an unrec duced state in the residue in the furnace.

l claim:

l. il method lor making lead from lead orrido containing ravv materials which consists in heating the ravv material together tvith a solid reducing agent in a rotatingr revolving furnace, having a clear length not greater than its clear diameter and preheated to reaction temperatures, condensing the volatiliaed products and bringing them back into the furnace repeatedly, until the de aired yield ot lead is obtained.

Q.. Process ol separating non-volatile met als 'trom ores, smelter products and similar ravv materials which comprises charging the ravv material and a reducing agent into a revolving 'furnace preheated to reaction tem- 'i eratures the clear diameter of which is at least as great as its clear length, heating the inirture in the furnace while revolving the same to such a temperature that reduction talres place vvithin the charge, and supplying heat necessary tor further reduction by means oit a ilalne burning Within the :turnace in the presence of the charge.

d. Process as claimed in claim 2 wherein the 'llame is reversed and travels the length ot the furnace twice. l

il. Process as claimed in claim 2 `wherein the volatiiiaed products are recovered.

Process as claimed in claim 2 wherein the ravv material comprises an oxide of the group consisting oit lead oxide, copper oxide and tin caido.

ill method Afor making lead `trom lead orride containing ravfmaterials which coniorises heating the ravv material together With a carlooucontaining reducing agent in a rotating revolving furnace, having a clear length not greater than its clear diameter and preheated to reaction temperatures, condensing the volatilized products and bringing them bach into the furnace repeatedly, until the desired yield or. lead is obtained.

l. A method tor making lead from lead oxide containing ravir materials which comprises heating the raw material together with lead sulfide as reducing agent in a rotating revolving furnace, having a clear length not greater than its clear diameter and preheated to reaction temperatures,` condensing the volatilized products and bringing them back into the furnace repeatedly, until the desired yield of lead is obtained.

8. A process for separating non-volatile metals from ores smelter products and sirniu lar ravv materials which comprises heating the raw material in the presence ot a reducing agent to such a temperature that reduction takes place Within the charge in a preheated revolving urnace the clear diameter ot which is at least as great as its clear length and supplying heat necessary lor :turther reduction by means of a name burning Within the furnace in the presence ot the charge. g

9. Process as claimed in claim 8 wherein the 'Haine is reversed and travels the length ot the furnace twice.,

l0. Process as claimed in claim 8 wherein the volatilized products are recovered.

ln testimony vvhereol l attivi my signature.

JUSTUS KUHLMEYER. 

